Hydrodynamic behavior in a moving granular bed filter for modeling on char separation during the biomass fast pyrolysis process

Moving granular bed filters (MGBFs) are the promising approach to improve the quality of pyrolysis oil by removing char particles from fast pyrolysis vapor streams. To minimize the commercial MGBF system, the inner MGBF structures were modified, resulting in differential granular media velocities between inlet and outlet gas stream. The modified structure was applied to increase the removal efficiency under the same superficial gas velocity. The experiments were conducted at room temperature and the designed parameters included the insert length and angle of inserted plates in the bottom of MGBF. In this study, the insert plates were used to distinguish the MGBF into two particle flow streams in the same section. The section area was the function of particle response angle, insert length, insert angle, and angle of the MGBF boundary plate. An accurate equation for determining the mass flow rate of the bed material particle and section area was proposed in this study. In addition, cold model filter tests were conducted on differential designs for three sets of flow fields. These results show that differential flow field designs can effectively enhance filtration efficiency. Under the same filtration pressure decline or loss, the filtration efficiency can be increased from the baseline of 95.4% to 99.9%.